mybatis oracle BLOB类型字段保存与读取

一、BLOB字段
　　BLOB是指二进制大对象也就是英文Binary Large Object的所写，而CLOB是指大字符对象也就是英文Character Large Object的所写。其中BLOB是用来存储大量二进制数据的；CLOB用来存储大量文本数据。BLOB通常用来保存图片、文件等二进制类型的数据。

二、使用mybatis操作blob

　　1、表结构如下：

create table BLOB_FIELD
(
   ID                   VARCHAR2(64 BYTE)    not null,
   TAB_NAME             VARCHAR2(64 BYTE)    not null,
   TAB_PKID_VALUE       VARCHAR2(64 BYTE)    not null,
   CLOB_COL_NAME        VARCHAR2(64 BYTE)    not null,
   CLOB_COL_VALUE       CLOB,
   constraint PK_BLOB_FIELD primary key (ID)
);

　　2、实体代码如下：

 package com.test.entity;

 import java.sql.Clob; 

 /**
  * 大字段
  */
 public class BlobField { 

     private String tabName;// 表名
     private String tabPkidValue;// 主键值
     private String blobColName;// 列名
     private byte[] blobColValue;// 列值 clob类型

     public String getTabName() {
         return tabName;
     }

     public void setTabName(String tabName) {
         this.tabName = tabName;
     }

     public String getTabPkidValue() {
         return tabPkidValue;
     }

     public void setTabPkidValue(String tabPkidValue) {
         this.tabPkidValue = tabPkidValue;
     }

     public String getBlobColName() {
         return blobColName;
     }

     public void setBlobColName(String blobColName) {
         this.blobColName = blobColName;
     }

     public byte[] getBlobColValue() {
         return blobColValue;
     }

     public void setBlobColValue(byte[] blobColValue) {
         this.blobColValue = blobColValue;
     }

 }

　　3、mybatis sql代码如下：

 <?xml version="1.0" encoding="UTF-8" ?>
 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 <mapper namespace="com.test.dao.BlobFieldDao">

     <sql id="blobFieldColumns">
         a.ID AS id,
         a.TAB_NAME AS tabName,
         a.TAB_PKID_VALUE AS tabPkidValue,
         a.BLOB_COL_NAME AS blobColName,
         a.BLOB_COL_VALUE AS blobColValue
     </sql>

     <sql id="blobFieldJoins">
     </sql>

     <select id="get" resultType="blobField">
         SELECT
         <include refid="blobFieldColumns" />
         FROM BLOB_FIELD a
         <include refid="blobFieldJoins" />
         WHERE a.ID = #{id}
     </select>

     <select id="findList" resultType="blobField">
         SELECT
         <include refid="blobFieldColumns" />
         FROM BLOB_FIELD a
         <include refid="blobFieldJoins" />
     </select> 

     <insert id="insert">
         INSERT INTO BLOB_FIELD(
         ID ,
         TAB_NAME ,
         TAB_PKID_VALUE ,
         BLOB_COL_NAME ,
         BLOB_COL_VALUE
         ) VALUES (
         #{id},
         #{tabName},
         #{tabPkidValue},
         #{blobColName},
         #{blobColValue,jdbcType=BLOB}
         )
     </insert>

     <update id="update">
         UPDATE BLOB_FIELD SET
         TAB_NAME = #{tabName},
         TAB_PKID_VALUE = #{tabPkidValue},
         BLOB_COL_NAME = #{blobColName},
         BLOB_COL_VALUE = #{blobColValue}
         WHERE ID = #{id}
     </update>
     <delete id="delete">
         DELETE FROM BLOB_FIELD
         WHERE ID = #{id}
     </delete>

 </mapper>

　　3、controller代码如下：

　　a、保存BLOB字段代码

 /**
      * 附件上传
      *
      * @param testId
      *            主表Id
      * @param request
      * @return
      * @throws UnsupportedEncodingException
      */
     @RequiresPermissions("exc:exceptioninfo:feedback")
     @RequestMapping(value = "attachment", method = RequestMethod.POST)
     @ResponseBody
     public Map<String, Object> uploadAttachment(@RequestParam(value = "testId", required = true) String testId, 

 HttpServletRequest request)
             throws UnsupportedEncodingException {
         Map<String, Object> result = new HashMap<String, Object>();

         MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
         // 获得文件
         MultipartFile multipartFile = multipartRequest.getFile("Filedata");// 与前端设置的fileDataName属性值一致
         String filename = multipartFile.getOriginalFilename();// 文件名称
         InputStream is = null;
         try {
             //读取文件流
             is = multipartFile.getInputStream();
             byte[] bytes = FileCopyUtils.copyToByteArray(is);
             BlobField blobField = new BlobField();
             blobField.setTabName("testL");
             blobField.setTabPkidValue(testId);
             blobField.setBlobColName("attachment");
             blobField.setBlobColValue(bytes);
             //保存blob字段
             this.testService.save(blobField, testId, filename);
             result.put("flag", true);
             result.put("attachmentId", blobField.getId());
             result.put("attachmentName", filename);
         } catch (IOException e) {
             e.printStackTrace();
             result.put("flag", false);
         } finally {
             IOUtils.closeQuietly(is);
         }
         return result;
     }    

　　b、读取BLOB字段

 /**
      * 下载附件
      *
      * @param attachmentId
      * @return
      */
     @RequiresPermissions("exc:exceptioninfo:view")
     @RequestMapping(value = "download", method = RequestMethod.GET)
     public void download(@RequestParam(value = "attachmentId", required = true) String attachmentId,
             @RequestParam(value = "attachmentName", required = true) String attachmentName, HttpServletRequest 

 request, HttpServletResponse response) {
         ServletOutputStream out = null;
         try {
             response.reset();
             String userAgent = request.getHeader("User-Agent");
             byte[] bytes = userAgent.contains("MSIE") ? attachmentName.getBytes() : attachmentName.getBytes("UTF-

 8"); // fileName.getBytes("UTF-8")处理safari的乱码问题
             String fileName = new String(bytes, "ISO-8859-1");
             // 设置输出的格式
             response.setContentType("multipart/form-data");
             response.setHeader("Content-Disposition", "attachment;fileName=" + URLEncoder.encode(attachmentName, 

 "UTF-8"));
             BlobField blobField = this.blobFieldService.get(attachmentId);
             //获取blob字段
             byte[] contents = blobField.getBlobColValue();
             out = response.getOutputStream();
             //写到输出流
             out.write(contents);
             out.flush();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }                                

　　本例子将文件上传并保存到BLOB类型字段字段，下载的时候读取BLOB字段，并写入成输出流。